[PATCH] drm/vmwgfx: integer underflow in vmw_cmd_dx_set_shader() leading to an invalid read

[Murray McAllister]

If SVGA_3D_CMD_DX_SET_SHADER is called with a shader ID
of SVGA3D_INVALID_ID, and a shader type of
SVGA3D_SHADERTYPE_INVALID, the calculated binding.shader_slot
will be 4294967295, leading to an out-of-bounds read in vmw_binding_loc()
when the offset is calculated.

Signed-off-by: Murray McAllister <murray.mcallis...@gmail.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c 
b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
index 2ff7ba04d8c8..9aeb5448cfc1 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
@@ -2193,7 +2193,8 @@ static int vmw_cmd_dx_set_shader(struct vmw_private 
*dev_priv,
 
        cmd = container_of(header, typeof(*cmd), header);
 
-       if (cmd->body.type >= SVGA3D_SHADERTYPE_DX10_MAX) {
+       if (cmd->body.type >= SVGA3D_SHADERTYPE_DX10_MAX ||
+           cmd->body.type < SVGA3D_SHADERTYPE_MIN) {
                VMW_DEBUG_USER("Illegal shader type %u.\n",
                               (unsigned int) cmd->body.type);
                return -EINVAL;
-- 
2.20.1